1. Field of the Invention
The present invention relates to a device and a method used in a wireless communication system, and more particularly, to a device and a method of handling a data transmission/reception for dual connectivity.
2. Description of the Prior Art
A long-term evolution (LTE) system provides high data rate, low latency, packet optimization, and improved system capacity and coverage. The LTE system is evolved continuously to increase peak data rate and throughput by using advanced techniques, such as carrier aggregation (CA), dual connectivity, licensed-assisted access, etc. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes at least one evolved Node-B (eNB) for communicating with at least one user equipment (UE), and for communicating with a core network. The core network may include a mobility management and a Quality of Service (QoS) control of the at least one UE.
A UE may be configured dual connectivity, i.e., is connected to a master eNB (MeNB) and a secondary eNB (SeNB). The MeNB (i.e., source MeNB) may initiate an inter-MeNB handover, and a target MeNB may decide to keep the SeNB. When the UE receives a handover command and the handover command involving a SCG change, the UE updates a S-KeNB key and a KeNB key. However, it is not known which one of the S-KeNB key and the KeNB key should be updated first by the UE.
According to the prior art, when the UE receives a handover command and the handover command involving a SCG change, the UE may perform a random access procedure to the SeNB first and then may perform a random access procedure to the MeNB. Completeness of handover is delayed and possibility of a handover failure is increased, since the UE transmits an RRCConnectionReconfigurationComplete to the MeNB after successfully completing the random access procedure to the SeNB.
Thus, how to handle a data transmission/reception for dual connectivity is an important problem to be solved.